﻿using System;

class Program
{
    static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        int k = int.Parse(Console.ReadLine());
        int kn=k-n;
        float fn = 1;
        float fk = 1;
        float fkn = 1;
        double result;
        do
        {
            fn *= n;
            n--;
        }
        while (n > 0);
        do
        {
            fk *= k;
            k--;
        }
        while (kn > 0);
        do
        {
            fkn *= kn;
            kn--;
        }
        while (kn > 0);
        result = (fn * fk) / fkn;
        Console.WriteLine(result);
    }
}